Observability platform that finds AI agent failures in live production traffic, ranks them by severity, and hands fixes to your coding agent.
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1 / 2Overview
What is three.dev?
Find out how your AI agent fails. Before your users do.
Almost every team now runs AI in production, but few know how it behaves once real users show up. The failures are quiet: a wrong refund policy, a made-up order status. Nothing crashes, so you hear about it from your users.
three.dev finds those failures in your live traffic on its own and ranks them by severity. Setup is one prompt to Claude Code, Cursor or Codex. Then your coding agent gets what it needs to write the fix. The Free plan includes 50,000 requests a month, and a launch offer gives six months of Starter free for teams that sign up by November 22, 2026.
Platforms and languages
three.dev Availability
Platforms
Languages
Capabilities
three.dev Key Features
Failure discovery
Scores live production traffic and finds failing agent conversations on its own.
Ranked failure modes
Groups failures by root cause and ranks them by frequency and severity.
Fix handoff via MCP
Your coding agent pulls failure details over MCP and writes the fix.
Verify improvements
Compare traffic slices and prompt versions before and after a fix.
Evidence for every issue
Each problem points at the exact line in the system prompt or message that caused it.
Best for
Who uses three.dev?
Teams running AI agents in production
Find and fix agent failures in live traffic before users report them
Plans and access
three.dev Pricing
Freemium
Free $0; Starter $79/mo; Pro $249/mo
Common questions
three.dev FAQs
What counts as processed data?
Processed data is the live traffic three.dev scores — requests, messages and the context around them.
What counts as a scoring request?
Each evaluation of an agent conversation counts as one scoring request against your plan.
What are the Free plan limits?
The Free plan covers 50,000 requests a month, 1 GB of data, 5,000 scorings and 30 days of history, with unlimited seats.
How does the launch offer work?
Teams that sign up by November 22, 2026 get six months of the Starter plan free.
Do you charge per seat?
No. Every plan includes unlimited seats.
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